1. Field of Invention
The present invention relates to an inductor and fabricating method thereof, more particularly, to an inductor formed on a semiconductor substrate where other semiconductor devices are formed and a fabricating method thereof.
2. Discussion of Related Art
In general, a circuit includes transistors, resistors, capacitors, and/or inductors. It is difficult to fabricate an inductor on the same semiconductor substrate where transistors, resistors, and capacitors are formed because of its substantially planar, coiled shape. Despite such difficulty, techniques of fabricating inductors on a semiconductor substrate along with transistors, resistors, and capacitors are studied by designers who design circuitry and semiconductor chips.
A technique of forming inductors with transistors, resistors, capacitors on the same semiconductor substrate is disclosed by Chan M. Desaigoudar in U.S. Pat. No. 5,370,766. Inductors of the related art are fabricated by forming an insulating layer on a substrate, and then forming the inductors from electrically-conductive substances such as Al, Au, Ag and the like on the insulating layer.
In this case, the inductors are formed to have coiled shapes by patterning a conductive substance having been deposited on an insulating layer. Then, inductor coil terminal pads, which connect the inductors through vias to neighbouring capacitors, transistors or the like to constitute a circuit, are formed. The inductor coil terminal pads are formed between the substrate and the inductors.
As mentioned in the above description, inductors are fabricated by the processes of forming transistors, resistors, and capacitors on a semiconductor substrate in the related art. Unfortunately, the surface area of the inductors are large because the inductors of the related art are formed on the semiconductor substrate as a two-dimensional coil.
In contrast to the prior art""s substantially planar coil-shaped inductors, the inductor according to the present invention is a three-dimensional spiral structure. In the method according to the present invention, conductive segments forming the bottom portion of each loop in the spiral are formed by ion-implantation into a semiconductor layer. The conductive segments are spaced apart in a first direction. A first dielectric layer crossing the mid portions of these conductive segments is formed to have a strip-like shape extending in the first direction. A conductive core is then formed on the first dielectric layer. A second dielectric layer is formed over the semiconductor layer, and two contact holes for each conductive segment are formed in the second dielectric layer. One contact hole exposes a portion of the conductive segment on one side of the first dielectric layer, and the other contact hole exposes a portion of the conductive segment on the other side of the first dielectric layer. Metal is then deposited over the second dielectric layer so that the contact holes are filled, and the metal is etched to form conductive pattern segments, which form the top and side portions of each loop in the inductor. Specifically, the conductive pattern segment connects one side of one conductive segment to the other side of the next conductive segment.
Accordingly, an inductor formed according to the present invention can be formed on the same semiconductor substrate from which other devices are fabricated, and because of its three-dimensional structure, the inductor takes up significantly less surface area than conventional inductors.